The 50 most-cited articles in The Analyst, 2017

Machine learning methods have found many applications in Raman spectroscopy, especially for the identification of chemical species. However, almost all of these methods require non-trivial preprocessing such as baseline correction and/or PCA as an essential step. Here we describe our unified solution for the identification of chemical species in which a convolutional neural network is trained to automatically identify substances according to their Raman spectrum without the need for preprocessing. We evaluated our approach using the RRUFF spectral database, comprising mineral sample data. Superior classification performance is demonstrated compared with other frequently used machine learning algorithms including the popular support vector machine method.

Recent studies have shown that microdroplet reactions are markedly accelerated compared to the corresponding bulk-phase reactions. This raises the question whether all reactions can be sped up by this means. We present a counter example, and we show that the reaction mechanism in microdroplets can differ sharply from that in bulk, especially because of the distinct microdroplet surface environment. This analysis helps to guide us how to choose and control reactions in microdroplets and provides a possible perspective on utilizing microdroplet chemistry to scale up synthesis.

Mass spectrometry is being used in many clinical research areas ranging from toxicology to personalized medicine. Of all the mass spectrometry techniques, mass spectrometry imaging (MSI), in particular, has continuously grown towards clinical acceptance. Significant technological and methodological improvements have contributed to enhance the performance of MSI recently, pushing the limits of throughput, spatial resolution, and sensitivity. This has stimulated the spread of MSI usage across various biomedical research areas such as oncology, neurological disorders, cardiology, and rheumatology, just to name a few. After highlighting the latest major developments and applications touching all aspects of translational research (i.e. from early pre-clinical to clinical research), we will discuss the present challenges in translational research performed with MSI: data management and analysis, molecular coverage and identification capabilities, and finally, reproducibility across multiple research centers, which is the largest remaining obstacle in moving MSI towards clinical routine.

The exhaustive body of literature published in the last four years on the development and application of systems based on surface-enhanced Raman spectroscopy (SERS) combined with microfluidic devices demonstrates that this research field is a current hot topic. This synergy, also referred to as lab-on-a-chip SERS (LoC-SERS) or nano/micro-optofluidics SERS, has opened the door for new opportunities where both techniques can profit. On the one hand, SERS measurements are considerably improved because the processes previously performed on a large scale in the laboratory and prone to human error can now be carried out in nanoliter volumes in an automatic and reproducible manner; on the other hand, microfluidic platforms need detection methods able to sense in small volumes and therefore, SERS is ideal for this task. The present review not only aims to provide the reader an overview of the recent developments and advancements in this field, but it also addresses the key aspects of fundamental SERS theory that influence the interpretation of SERS spectra, as well as the challenges brought…

While NMR is the most used analytical method for determining the molecular structure of isolated chemical entities, small compounds as well as macromolecules, its capability of analysing complex mixtures is less known. The advent of Diffusion Ordered SpectroscopY (DOSY) NMR has made diffusion experiments popular, enabling diffusion coefficients to be routinely measured and used to characterize chemical systems in solution. Indeed, since the translational diffusion coefficients of molecular species reflect their effective sizes and shapes, DOSY NMR allows the separation of the chemical entities present in multicomponent systems and, as in all diffusion NMR experiments, provides information on their intermolecular interactions as well as on their size and shape. The main aim of this review is to present an overview of the DOSY NMR mapping and its applications. The paper starts with a brief introduction to pulsed-field gradient (PFG) NMR and then focuses on the methodological procedures that can be used to perform good diffusion data acquisition and to obtain good-quality DOSY maps.…

Oncological applications of Raman spectroscopy have been contemplated, pursued, and developed at academic level for at least 25 years. Published studies aim to detect pre-malignant lesions, detect cancer in less invasive stages, reduce the number of unnecessary biopsies and guide surgery towards the complete removal of the tumour with adequate tumour resection margins. This review summarizes actual clinical needs in oncology that can be addressed by spontaneous Raman spectroscopy and it provides an overview over the results that have been published between 2007 and 2017. An analysis is made of the current status of translation of these results into clinical practice. Despite many promising results, most of the applications addressed in scientific studies are still far from clinical adoption and commercialization. The main hurdles are identified, which need to be overcome to ensure that in the near future we will see the first Raman spectroscopy-based solutions being used in routine oncologic diagnostic and surgical procedures.

Biomarkers refer to analytes that can be used in the diagnosis of diseases or disorders. In saliva, there are many components that are potential biomarkers, and increasing research has focussed on the development of saliva as a diagnostic fluid. This review summarizes the existing uses of salivary biomarkers and highlights the importance of the choice of saliva collection as well as the storage procedures. A case study on the effect of collection tools on the concentrations of one of the potential biomarkers, glutathione, is highlighted. Moreover, molecular diagnosis requires reliable measurement assays. This review presents electroanalytical methods for the detection of salivary biomarkers. It further reviews approaches that can be taken to improve the selectivity of electroanalytical assays without the use of biologically selective materials, notably without the use of enzymes or antibodies.

were carried out at the bare glassy carbon working electrode. This method enabled sensitive detection of 100 exosomes per μL with a relative standard deviation (%RSD) of <5.5% in cancer cell lines and a small cohort of serum samples (n = 9) collected from patients with colorectal adenocarcinoma. We believe that our approach could potentially represent an effective bioassay for the quantification of disease-specific exosomes in clinical samples.

The inherent heterogeneity in cell populations has become of great interest and importance as analytical techniques have improved over the past decades. With the advent of personalized medicine, understanding the impact of this heterogeneity has become an important challenge for the research community. Many different microfluidic approaches with varying levels of throughput and resolution exist to study single cell activity. In this review, we take a broad view of the recent microfluidic developments in single cell analysis based on microwell, microchamber, and droplet platforms. We cover physical, chemical, and molecular biology approaches for cellular and molecular analysis including newly emerging genome-wide analysis.

Field-Effect Transistor sensors (FET-sensors) have been receiving increasing attention for biomolecular sensing over the last two decades due to their potential for ultra-high sensitivity sensing, label-free operation, cost reduction and miniaturisation. Whilst the commercial application of FET-sensors in pH sensing has been realised, their commercial application in biomolecular sensing (termed BioFETs) is hindered by poor understanding of how to optimise device design for highly reproducible operation and high sensitivity. In part, these problems stem from the highly interdisciplinary nature of the problems encountered in this field, in which knowledge of biomolecular-binding kinetics, surface chemistry, electrical double layer physics and electrical engineering is required. In this work, a quantitative analysis and critical review has been performed comparing literature FET-sensor data for pH-sensing with data for sensing of biomolecular streptavidin binding to surface-bound biotin systems. The aim is to provide the first systematic, quantitative comparison of BioFET results for a…

With the rapid development of DNA nanotechnology, various DNA nanostructures with different shapes and sizes have been self-assembled using "bottom-up" fabrication strategies and applied to a wide range of fields such as biosensors, drug delivery and tools for molecular biology. As a classical and simple polyhedron, DNA tetrahedron can be easily synthesised by a one-step assembly. Due to the excellent biocompatibility and cellular permeability, it provides a universal and promising platform to construct a series of biosensors and drug delivery systems for living cells studies. Moreover, the high programmability of DNA tetrahedron determines its capability to perform artful design and combine with other materials. Herein, we review and summarise the development and applications of DNA tetrahedron in living cell studies. We mainly focus on two parts, cellular biosensors for the detection of nucleic acids, proteins, small molecules and cancer cells and drug delivery systems for chemotherapy, immunotherapy, photodynamic therapy and gene silencing. With the rapid progress in DNA…

We report the application of machine learning to smartphone-based colorimetric detection of pH values. The strip images were used as the training set for Least Squares-Support Vector Machine (LS-SVM) classifier algorithms that were able to successfully classify the distinct pH values. The difference in the obtained image formats was found not to significantly affect the performance of the proposed machine learning approach. Moreover, the influence of the illumination conditions on the perceived color of pH strips was investigated and further experiments were conducted to study the effect of color change on the learning model. Non-integer pH levels are identified as their nearest integer pH values, whereas the test results for integer pH levels using JPEG, RAW and RAW-corrected image formats captured under different lighting conditions lead to perfect classification accuracy, sensitivity and specificity, which proves that colorimetric detection using machine learning based systems is able to adapt to various experimental conditions and is a great candidate for smartphone-based…

Structures for lossless ion manipulations (SLIM) provide a new paradigm for efficient, complex and extended gas phase ion manipulations. SLIM are created from electric fields generated by the application of DC and RF potentials to arrays of electrodes patterned on two parallel surfaces. The electric fields provide lossless ion manipulations, including effective ion transport and storage. SLIM modules have been developed using both constant and oscillatory electric fields (e.g. traveling waves) to affect the ion motion. Ion manipulations demonstrated to date with SLIM include: extended trapping, ion selection, ion dissociation, and ion mobility spectrometry (IMS) separations achieving unprecedented ultra high resolution. SLIM thus provide the basis for previously impractical manipulations, such as very long path length ion mobility separations where ions traverse a serpentine path multiple times, as well as new capabilities that extend the utility of these developments based on temporal and spatial compression of ion mobility separations and other ion distributions. The evolution of…

This review article describes the significant recent advances in the analysis of proteins by capillary and microchip electrophoresis during the period from mid-2014 to early 2017. This review highlights the progressions, new methodologies, innovative instrumental modifications, and challenges for efficient protein analysis in human specimens, animal tissues, and plant samples. The protein analysis fields covered in this review include analysis of native, reduced, and denatured proteins in addition to Western blotting, protein therapeutics and proteomics.

Proteases play a pivotal role in regulating important physiological processes from food digestion to blood clotting. They are also important biomarkers for many diseases such as cancers. The importance of proteases has led to extensive efforts in the screening of proteases and their inhibitors as potential drug molecules. For example, human immunodeficiency virus (HIV) patients have been treated with HIV-1 protease inhibitors to prolong the life expectancy of patients. Such a close relationship between diseases and proteases provides a strong motivation for developing sensitive, selective, and robust protease assays and sensors, which can be exploited to discover new proteases and inhibitors. In this aspect, protease assays based on levels of proteolytic activities are more relevant than protease affinity assays such as immunoassays. In this review, recent developments of protease activity assays based on different detection principles are discussed and compared. For homogenous assays, fluorescence-based techniques are the most popular due to their high sensitivity and quantitative…

Charge detection mass spectrometry (CDMS) is a single molecule method where the mass of each ion is directly determined from individual measurements of its mass-to-charge ratio and charge. CDMS is particularly valuable for the analysis of high mass and heterogeneous analytes, where conventional MS methods are often confounded. In the last few years, CDMS has received a renaissance. Technical developments have improved the resolution and dramatically increased the breadth of problems that can be addressed. These improvements have moved CDMS more into the mainstream as interest in the application of mass spectrometry to high molecular weight species has grown. In the article, the three main variants of CDMS are described, along with an overview of recent applications.

Protein glycosylation is a common post-translational modification that has significant impacts on protein folding, lifespan, conformation, distribution and function. N-Glycans, which are attached to asparagine residues of proteins, are studied most often due to their compatibility with enzymatic release. Despite the ease of N-glycan release, compositional and structural complexity coupled with poor ionization efficiency during liquid chromatography mass spectrometry (LC-MS) make quantitative glycomic studies a significant challenge. To overcome these challenges, glycans are almost always derivatized prior to LC-MS analyses to impart favorable characteristics, such as improved ionization efficiency, increased LC separation efficiency and the production of more informative fragments during tandem MS. There are a number of derivatization methods available for LC-MS analysis of glycans, each of which imparts different properties that affect both glycan retention on LC columns and MS analyses. To provide guidance for the proper selection of derivatizing reagents and LC columns, herein,…

Native mass spectrometry can provide insight into the structure of macromolecular biological systems. As analytes under investigation get larger and more complex, instrument capabilities need to be advanced. Herein, modifications to an Orbitrap Q Exactive Plus mass spectrometer that increase signal intensity, mass resolution, and maximum m/z measurable are described.

A rapid method for the quantitation of sixteen neutral and acidic monosaccharides, from both animal and plant sources was developed using ultra-high performance liquid chromatography triple quadrupole mass spectrometry (UHPLC/QqQ-MS) in dynamic multiple reaction monitoring (dMRM) mode. Monosaccharides including three pentoses (ribose, xylose, arabinose), two deoxyhexoses (rhamnose, fucose), five hexoses (fructose, mannose, allose, glucose, galactose), two hexuronic acids (glucuronic acid, galacturonic acid), and two N-acetyl-hexosamines (GlcNAc, GalNAc), were derivatized with 1-phenyl-3-methyl-5-pyrazolone (PMP), while underivatized sialic acids, Neu5Ac and Neu5Gc, were simultaneously analyzed with a 10-minute run. With the optimized UHPLC conditions, baseline separations of the isomers were achieved. The sensitivity and calibration ranges of this method were determined. The limits of detection were between femtomoles and attomoles with linear ranges spanning four to six orders of magnitude and coefficients of variation (CVs) ≤7.2%. Spiking experiments performed on a pooled fecal…

A microneedle electrochemical biosensor for the minimally invasive detection of organophosphate (OP) chemical agents is described. The new sensor relies on the coupling of the effective biocatalytic action of organophosphorus hydrolase (OPH) with a hollow-microneedle modified carbon-paste array electrode transducer, and involves rapid square-wave voltammetric (SWV) measurements of the p-nitrophenol product of the OPH enzymatic reaction in the presence of the OP substrate. The scanning-potential SWV transduction mode offers an additional dimension of selectivity compared to common fixed-potential OPH-amperometric biosensors. The microneedle device offers a highly linear response for methyl paraoxon (MPOx) over the range of 20-180 μM, high selectivity in the presence of excess co-existing ascorbic acid and uric acid and a high stability sensor upon exposure to the interstitial fluid (ISF). The OPH microneedle sensor was successfully tested ex vivo using mice skin samples exposed to MPOx, demonstrating its promise for minimally-invasive monitoring of OP agents and pesticides and as a…

Molecular profiling of single cells has the potential to significantly advance our understanding of cell function and cellular processes of importance to health and disease. In particular, small molecules with rapid turn-over rates can reveal activated metabolic pathways resulting from an altered chemical environment or cellular events such as differentiation. Consequently, techniques for quantitative metabolite detection acquired in a higher throughput manner are needed to characterize the biological variability between seemingly homogenous cells. Here, we show that nanospray desorption electrospray ionization (nano-DESI) mass spectrometry (MS) enables sensitive molecular profiling and quantification of endogenous species in single cells in a higher throughput manner. Specifically, we show a large number of detected amino acids and phospholipids, including plasmalogens, readily detected from single cheek cells. Further, by incorporating a phosphatidylcholine (PC) internal standard into the nano-DESI solvent, we determined the total amount of PC in one cell to be 1.2 pmoles.…

While global metabolic profiling (untargeted metabolomics) has been the center of much interest and research activity in the past few decades, more recently targeted metabolomics approaches have begun to gain ground. These analyses are, to an extent, more hypothesis-driven, as they focus on a set of pre-defined metabolites and aim towards their determination, often to the point of absolute quantification. The continuous development of the technological platforms used in these studies facilitates the analysis of large numbers of well-characterized metabolites present in complex matrices. The present review describes recent developments in the hyphenated chromatographic methods most often applied in targeted metabolomic/lipidomic studies (LC-MS/MS, CE-MS/MS, and GC-MS/MS), highlighting applications in the life and food/plant sciences. The review also underlines practical challenges-limitations that appear in such approaches.

As a superb tool to visualize and study the spatial-temporal distribution of chemicals, Raman microscopy has made a big impact in many disciplines of science. While label-free imaging has been the prevailing strategy in Raman microscopy, recent development and applications of vibrational/Raman tags, particularly when coupled with stimulated Raman scattering (SRS) microscopy, have generated intense excitement in biomedical imaging. SRS imaging of vibrational tags has enabled researchers to study a wide range of small biomolecules with high specificity, sensitivity and multiplex capability, at a single live cell level, tissue level or even in vivo. As reviewed in this article, this platform has facilitated imaging distribution and dynamics of small molecules such as glucose, lipids, amino acids, nucleic acids, and drugs that are otherwise difficult to monitor with other means. As both the vibrational tags and Raman instrumental development progress rapidly and synergistically, we anticipate that this technique will shed light onto an even broader spectrum of biomedical problems.

Pathogens are key contaminants in water that are responsible for the generation of various water-borne diseases, and include viruses, fungi, bacteria, and protozoan parasites. The pathogenic effects of these species in water depend on their shape, size, composition, and structure. The resulting water-borne diseases are a serious threat to the environment, including to humans and animals, and are directly responsible for environmental deterioration and pollution. The potential presence of these pathogens requires sensitive, powerful, efficient, and ideally real-time monitoring methods for their reproducible quantification. Conventional methods for pathogen detection mainly rely on time-consuming enrichment steps followed by biochemical identification strategies, which require assay times ranging from 24 h to up to a week. However, in recent years, significant efforts have been made towards the development of biosensing technologies enabling rapid and close-to-real-time detection of water-borne pathogens. This review summarizes recent developments in biosensors and sensing systems…

In this review we present the state of the art and the most recent advances in the field of optical sensing with hybrid plasmonic-photonic whispering gallery mode (WGM) resonators. After a brief introduction on the basic physics behind photonic WGM resonators and localized surface plasmon (LSP) nanostructures, we analyze the different types of optical sensors specifically designed for bulk refractive index sensing, molecular binding and single object detection. We point out the physical and technological key points of the different approaches proposed in the literature, and we systematically compare hybrid sensors and purely photonic WGM sensors. This comparative analysis points out the real advantages brought by LSP nanostructures, and it identifies the most promising hybrid architectures.

were 0.02 μM, 0.009 μM, and 0.02 μM for acetamiprid. Most interestingly, the AuNP/MOF-199 composites, whose morphology was long tube sheet, exhibited excellent SERS activity. These novel composites with high sensitivity, stability, and reproducibility provide a new route for the detection of pesticides via the SERS technology.

The accessibility of particle-coupled antibodies is important for many analytical applications, but comprehensive data on parameters controlling the accessibility are scarce. Here we report on the site-specific accessibility of monoclonal antibodies, immobilized on magnetic nanoparticles (500 nm) by the widely used covalent EDC coupling method, with the variation of four key coupling parameters (surface activation and immobilization pH, crosslinker and antibody concentration ratios). By developing quantitative radio-labelled assays, the number of immobilized antibodies, the Fab domain accessibility (in a sandwich immunoassay), and the Fc domain accessibility (in a Protein G assay) were determined. For sub-monolayer surface coverage, the observed numbers of accessible Fab and Fc domains are equal and scale linearly with the antibody density. For above monolayer coverage, the fractions of accessible Fab and Fc domains decrease, in an unequal manner. The results show that the antibody accessibility is primarily determined by the antibody surface density, rather than by chemical…

For the successful treatment of infections, real-time analysis and enhanced multiplex capacity, sensitivity and cost-effectiveness of the developed detection method are critical. In this work, surface-enhanced Raman scattering (SERS) was employed with the final aim of identification and discrimination of pathogenic bacteria, based on their detected SERS fingerprint at the single-cell level. Several genera of bacteria that are found in most of the isolated infections in bacteraemia were successfully identified in less than 5 minutes without the use of antibodies or other specific receptors. The key element of the SERS direct detection platform is the SERS substrate, which combines easy production at low costs with a high enhancement enabling single-cell detection. The innovative approach of detection required the in situ synthesis of silver nanoparticles (NPs), ensuring an intimate contact with the bacterial membrane. This protocol provided a good reproducibility of the single-cell SERS spectra and was successfully applied both on Gram-negative and Gram-positive microorganisms (E.…

The latest clinical procedures for the timely and cost-effective diagnosis of chronic and acute clinical conditions, such as cardiovascular diseases, cancer, chronic respiratory diseases, diabetes or sepsis (i.e. the biggest causes of death worldwide), involve the quantitation of specific protein biomarkers released into the blood stream or other physiological fluids (e.g. urine or saliva). The clinical thresholds are usually in the femtomolar to picolomar range, and consequently the measurement of these protein biomarkers heavily relies on highly sophisticated, bulky and automated equipment in centralised pathology laboratories. The first microfluidic devices capable of measuring protein biomarkers in miniaturised immunoassays were presented nearly two decades ago and promised to revolutionise point-of-care (POC) testing by offering unmatched sensitivity and automation in a compact POC format; however, the development and adoption of microfluidic protein biomarker tests has fallen behind expectations. This review presents a detailed critical overview into the pipeline of…

, which is much lower than that of conventional enzyme-linked immunosorbent assay (ELISA). Moreover, the method is validated for the analysis of 10 PSA clinical serum specimens, and the results agree very well with those obtained by using a commercialized ELISA kit. Therefore, this new, facile and efficient immunoassay is a promising technique with potential applications in medical science research and clinical diagnosis.

Highly homogeneous multi-element gelatin calibration standards were fabricated for quantitative LA-ICP-MS bioimaging. Heterogeneity issues caused by the so-called "coffee-stain" and/or "Marangoni" effects were found to be element-dependent but could be circumvented by careful selection of drying/setting conditions. A micro-homogeneity test was developed for certification of the standards.

Cloth fabrics and smartphones have become the two things people are most familiar with. Particularly, smartphones are used as portable personal computers, revolutionizing communication and lifestyle. Here, screen-printing technology is applied to fabricate carbon electrodes and electrochemical chambers on a single hydrophilic cloth, while the cloth-based electrochemiluminescence (ECL) signals are read out by using an inexpensive smartphone. Therefore, the ECL detection is available in both low-cost disposable sensors and a portable format, which may be very suitable to be used as a non-invasive monitoring tool for medical diagnostics. As a proof-of-principle, lactate oxidase is immobilized onto the working electrode for the lactate measurement. Under optimized conditions, the lactate levels can be quantified over the range of 0.05-2.5 mM, with a detection limit of 0.035 mM and the relative standard deviations of 4.7%, 5.2% and 5.0% for 0.05, 0.5 and 2.5 mM lactate (n = 5). In addition, the proposed biosensor has an acceptable stability and selectivity. Finally, the ECL biosensor is…

Polymerase Chain Reaction (PCR) is a critical tool for biological research investigators but recently it also has been making a significant impact in clinical, veterinary and agricultural applications. Plasmonic PCR, which employs the very efficient heat transfer of optically irradiated metallic nanoparticles, is a simple and powerful methodology to drive PCR reactions. The scalability of next generation plasmonic PCR technology will introduce various forms of PCR applications ranging from small footprint portable point of care diagnostic devices to large footprint central laboratory multiplexing devices. In a significant advance, we have introduced a real time plasmonic PCR and explored the ability of ultra-fast cycling compatible with both label-free and fluorescence-based monitoring of amplicon production. Furthermore, plasmonic PCR has been substantially optimized to now deliver a 30 cycle PCR in 54 seconds, with a detectable product. The advances described here will have an immediate impact on the further development of the use of plasmonic PCR playing a critical role in rapid…

The development of a simple, low-cost, time-saving and universally applicable method to monitor the progression of aptamer selection is particularly challenging. Herein, a combined strategy dependent on quantitative polymerase chain reaction amplification curve (AC) and melting curve analysis (MCA) is developed to monitor the convergence of the aptamer species during selection progress. As a parallel and complementary method to affinity tests and binding analyses, the AC-MCA method can be used to achieve the DNA complexity assay when affinity is undetectable. It is independent of the target properties and SELEX methods. Therefore, it has been demonstrated as a universal monitoring tool in different SELEX methods towards different targets (small molecules, proteins, bacteria and cancer cells). The AC-MCA method will facilitate current new aptamer discovery and aptamer-based wide application.

Since the introduction of desorption electrospray ionization (DESI) mass spectrometry (MS), ambient MS methods have seen increased use in a variety of fields from health to food science. Increasing its popularity in metabolomics, ambient MS offers limited sample preparation, rapid and direct analysis of liquids, solids, and gases, in situ and in vivo analysis, and imaging. The metabolome consists of a constantly changing collection of small (<1.5 kDa) molecules. These include endogenous molecules that are part of primary metabolism pathways, secondary metabolites with specific functions such as signaling, chemicals incorporated in the diet or resulting from environmental exposures, and metabolites associated with the microbiome. Characterization of the responsive changes of this molecule cohort is the principal goal of any metabolomics study. With adjustments to experimental parameters, metabolites with a range of chemical and physical properties can be selectively desorbed and ionized and subsequently analyzed with increased speed and sensitivity. This review covers the broad…

) were attained for most of the investigated analytes with total analysis times under 2 min per sample. Furthermore, we explored the suitability of this technology for on-site rapid molecular profiling of complex matrices. As a proof-of-concept, we demonstrate the rapid identification of milk samples from assorted animal and vegetal sources.

Array-based sensing methods can be used to distinguish sets of similar analytes, by using a number of non-specific or cross-reactive probes. Following subsequent statistical analysis, patterns or components can be isolated that can be used to unambiguously identify the specific analyte(s) present. Over the past two decades, various arrays for the identification of cations and anions have been reported. These often employ fluorescence methods, owing to good sensitivity and a versatile, easy to read output. The past few years have seen an increase in the number of such studies reported in the literature. This critical review will summarise this recent work, and identify the criteria required for a successful array system. In particular, it will focus on the different types of molecular structures that can be used, the breadth of ions that can be distinguished in a single array, the sensitivity and dynamic range to which they can be identified, and how successfully these aims have been met.

Reversible covalent binding of boronic acids with polyols and Lewis bases has facilitated the development of robust chemosensors for many biologically important species under physiologically or environmentally relevant conditions. This minireview covers selected examples of advances reported in this area from 2014 to 2016. While the discovery of new boron-containing binding motifs and identification of new analytical targets have expanded the ultility of boronic acid-based molecular recognition, unconventional sensing strategies such as exploitation of nanoscale self-assembly, multicomponent dynamic covalent assembly, and coupling boronate ester formation with a further chemical reaction have led to significantly improved sensor performance, enabling real-world applications in various areas such as cell biology and asymmetric catalysis.

, which displayed efficient peroxidase-like activity and high catalytic stability against temperature. The catalytic mechanism of the CuO/Pt nanocomposites was investigated by hydroxyl radical detection. The peroxidase-like activity decreased significantly in the presence of AA. On the basis of the inhibition property, a colorimetric biosensor was constructed by using the CuO/Pt nanocomposites for the detection of AA. It showed a high selectivity against amino acids, carbohydrates and normal ions. Thus, this work provides new insights into the application of inorganic nanocomposite-based nanozymes in the biosensing field.

A lateral flow strip biosensor for fast, sensitive, low-cost and on-site detection of kanamycin was developed by using kanamycin-specific aptamer-modified gold nanoparticles (AuNPs-apt) as a probe and oligonucleotide DNA1-modified silver nanoparticles (AgNPs-DNA1) as a signal amplification element. Through the complementary sequences of DNA1 and the aptamer, the AgNP-DNA1-apt-AuNPs complex can be formed and further captured on the test zone of the strip, where a capture probe DNA2 complementary to the 3'-terminal of DNA1 was immobilized. In the presence of kanamycin, it can competitively bind to the aptamer, and then inhibit the formation of the complex and the accumulation of AuNPs on the test zone. AuNPs-apt can finally be captured on the control zone via the specific binding between biotin and streptavidin. The assay avoids multiple incubation and washing steps and can be completed within 10 min. By observing the color change of the test zone, a qualitative detection for kanamycin can be achieved by the naked eye, with the visual limit of 35 nM. Meanwhile, a linear detection…

The number of patients suffering from cancer is constantly increasing and, consequently, the number of different chemotherapy treatments administered is increasing. Given the high reactivity and toxicity of antineoplastic drugs, analytical methods are required in all pharmaceutical fields, from drug development to their elimination in wastewater; including formulation quality control, environment and human exposure and therapeutic drug monitoring. The aim of this paper is to provide an overview of the analytical methods available for the determination of antineoplastic drugs in different matrices such as pharmaceutical formulations, biological and environmental samples. The applicability and performance of the reported methods will be critically discussed, with focus on the most commonly used antineoplastic drugs. Only conventional compounds and small molecules for targeted therapy will be considered in the present review.

This work presents a novel and facile strategy for the fabrication of gold-platinum bimetallic nanoclusters (Au-PtNCs) with adjustable Au/Pt molar ratios by a one-pot synthetic route. It was unexpectedly found that the prepared Au-PtNCs with an optimal Au/Pt molar ratio (1 : 1) could exhibit greatly enhanced peroxidase-like catalytic activity and chemical stability toward harsh conditions due to the synergistic effect of the two atoms, in contrast with pure AuNCs. These prominent advantages render Au-PtNCs capable of sensitive and selective colorimetric detection of glucose by means of a NCs-glucose oxidase (GOx) cascade-catalyzed system using 3,3',5,5'-tetramethylbenzidine (TMB) as a chromogenic substrate. This assay can be used not only for visual detection of glucose by the naked eye but for reliable and convenient quantification in the range from 5 to 55 μM with a detection limit of 2.4 μM. Importantly, to widen the application of point-of-care testing (POCT) of glucose to biomedical diagnosis, an integrated agarose hydrogel-based sensing platform comprising NCs, GOx and TMB was…

. Improved stability and robustness of the paper spray technique in the negative ion mode was achieved by the addition of chlorinated solvents. These applications demonstrate that paper spray mass spectrometry (PS-MS) can be used for rapid, sample preparation-free detection of chemical warfare agents and their hydrolysis products at physiologically relevant concentrations in biological samples.

In this study, a gas chromatography (GC) system was interfaced to a high-resolution Orbitrap mass spectrometer by means of an active capillary plasma ionization source, based on dielectric barrier discharge ionization (DBDI).

Composite particles containing the Zr-based metal-organic framework (MOF) UiO-66 were prepared using microwave-assisted solvothermal synthesis. Scanning electron microscopy, infrared spectroscopy, powder X-ray diffraction and nitrogen physisorption studies confirmed the deposition of 100-300 nm microporous particles with the UiO-66 topology on the surface of mesoporous 5 μm and non-porous 2.1 μm silica particles. The core-shell particles exhibited a unique flow-dependent separation selectivity (FDSS) effect which allows changes in both the retention and separation selectivity of small molecules by simple variation of the mobile phase flow rate under isocratic conditions. The impact of the loading of UiO-66 as well as the porosity of the underlying silica core (mesoporous and non-porous) on the FDSS effect was evaluated. The prepared adsorbents were also tested for the normal-phase (NP) and reversed-phase (RP) separation of xylene isomers, substituted benzenes and polyaromatic hydrocarbons (PAHs). Efficiencies of up to 32 400 plates per m (styrene, k 1.59) and 37 200 plates per m…

A miniaturized, robust, localized surface plasmon resonance (LSPR)-coupled fiber-optic (FO) nanoprobe providing an integrated and portable solution for detection of DNA hybridization and measurement of DNA concentrations has been demonstrated. The FO nanoprobe was created by constructing arrays of metallic nanostructures on the end facets of optical fibers utilizing nanofabrication technologies, including electron beam lithography and lift-off processes. The LSPR-FO nanoprobe device offers real-time, label-free, and low-sample-volume quantification of single-strand DNA in water with high sensitivity and selectivity, achieving a limit of detection around 10 fM. These results demonstrate the feasibility of the LSPR-FO nanoprobe device as a compact and low-cost biosensor for detection of short-strand DNA.

of a single multiply charged PEG molecule is demonstrated, and from these ion energy measurements and effects of collisions on the ion motion inside the trap, information about the ion mobility of the precursor ion and its fragments is obtained.

). Scores in the first principal component versus the hydrolysis time have been shown to provide an overview of the process dynamics related to protein structural changes. The herein presented results suggest that dry-film FTIR measurements have potential as a rapid tool for monitoring industrial protein hydrolysis processes.

The last few decades have witnessed the development of many high-performance separation methods that use biologically related binding agents. The combination of HPLC with these binding agents results in a technique known as high performance affinity chromatography (HPAC). This review will discuss the general principles of HPAC and related techniques, with an emphasis on their use for the analysis of biological compounds and pharmaceutical agents. Various types of binding agents for these methods will be considered, including antibodies, immunoglobulin-binding proteins, aptamers, enzymes, lectins, transport proteins, lipids, and carbohydrates. Formats that will be discussed for these methods range from the direct detection of an analyte to indirect detection based on chromatographic immunoassays, as well as schemes based on analyte extraction or depletion, post-column detection, and multi-column systems. The use of biological agents in HPLC for chiral separations will also be considered, along with the use of HPAC as a tool to screen or study biological interactions. Various examples…

can also be used for imaging in mice. The above applications make our new probe a potential chemical tool for the study of physiological and pathological functions of FA in cells and in vivo.